I don’t think it’s a joke: the Nazis believed all sorts of outlandish things. Now it comes out (why now?) that they had a project to train dogs to speak and perform military tasks. They wanted to create an army of Nazi dogs!
In 1998, I read The Lives of the Monster Dogs, a novel that takes place in Manhattan in 2008 when a bunch of walking, talking dogs, with Prussian accents, become celebrities. They escaped from a remote town founded by a Prussian officer hoping to do exactly what the Nazis wanted to do. I guess the author, Kirstin Bakis, scooped the news long ago.
And on the topic of talking dogs, Jim Thompson’s novel, The Golden Gizmo, a macabrely comic tale, features a deadly Doberman that talks and sings along with hymns.